Hitherto, an impact-type cutting machine is known in which a cutter shaft is installed eccentrically with respect to a drive shaft and rotates in conjunction with the drive shaft rotation, and a cutter into which the cutter shaft is inserted with play therebetween so as to rotate eccentrically by means of the action of centrifugal inertia resulting from the rotation of the drive shaft, whereby a surface to be cut is cut by the impact of an external peripheral surface of the cutter.
A floor cutting machine, which is an example of a conventional impact-type cutting machine, is designed to remove projecting portions of a floor surface, deposits, deteriorated floor coating materials, etc., and is arranged such that the rotation of a motor mounted on a base is transmitted to a drive shaft via a belt, and the drive shaft is thereby rotated to cut the floor surface. Two parallel flanges are secured to the drive shaft, and a plurality of cutter shafts are provided between the flanges at equal angular intervals therearound. A plurality of cutters are respectively provided on the cutter shafts in such a manner that each cutter shaft is inserted into a cutter with play (i.e. clearance) therebetween. The cutters are rotated eccentrically due to rotation of the drive shaft and, by virtue of the action of centrifugal inertia, apply the outer peripheral surfaces of the cutters impact against and cut the floor surface.
The hole for the insertion of a cutter shaft, which is provided in each cutter, is conventionally formed with a circular shape and, therefore, has had the following drawbacks:
(1) As the outer peripheral surface of a cutter is brought into contact with the floor surface, the cutter is separated from the cutter shaft and jumps at random around the cutter shaft, so that the impact force necessary for cutting is weakened, and the efficiency with which the floor surface is cut is poor. In addition, in order to increase the impact force with conventional cutters, it is necessary to increase the size of each cutter. Consequently, there is a drawback in that the cutting machine itself becomes larger, and its economic efficiency and operational efficiency are hence deteriorated. PA1 (2) The distance by which each cutter can be offset from its cutter shaft is small when compared with the size of the cutter, and the adaptability of the cutter to uneven portions of the floor surface is poor. Hence, it is difficult to cut relatively large recesses and, if a cutter is brought into contact with a projection, the cutter shaft is pushed upward, resulting in elastic deformation or breakage of the cutter shaft or the cutter.
Accordingly, an object of the present invention is to provide an improved cutter for an impact-type cutting machine which is capable of increasing the impact force imparted by a cutter against a floor surface by means of the force of centrifugal inertia, which improves the efficiency of cutting the floor surface, which is capable of preventing deformation or breakage of the cutter shaft and the cutter, and which can be made more compact and economically advantageous, thereby overcoming the above-described drawbacks.
To attain this object, the present invention provides a cutter for an impact-type cutting machine having a cutter shaft which is eccentrically provided on a drive shaft with respect to the drive shaft axis and is adapted to rotate around the drive shaft in conjunction with the rotation of the drive shaft, and a cutter into which the cutter shaft is inserted with play therebetween, wherein said cutter is provided with a hole for the insertion of the cutter shaft with play or clearance therebetween, which hole extends in the longitudinal direction of the cutter, and wherein a central portion of the hole substantially coincides with the center of gravity of the cutter.
In this arrangement as described above, when the drive shaft is rotated, the cutter shafts are rotated in conjunction with the rotation of the drive shaft, the action of centrifugal inertia is produced in the cutters, the impact force of the cutter against a floor surface becomes large, and the efficiency of cutting the floor surface is improved. At the same time, deformation or breakage of the cutter shaft or cutter is provented or minimized.